The field of the present invention is drainage systems for pleural cavities.
Air and liquid can enter the pleural cavity through a number of abnormal sources. The chest wall may have been punctured acidentally or through surgery, or the lung may have been punctured or cut. In either case, drainage of the pleural cavity is required. This need to drain the pleural cavity may exist for some time, requiring a drainage mechanism that may be left unattended with safety.
To provide a safe drainage mechanism which may be left on the patient, several features must be considered. First, it is desirable to have a water seal between the link to the pleural cavity and either atmosphere or a vacuum source. Even so, under extreme conditions when the plueral cavity for some reason has a lower pressure than the drainage unit, it is desirable to prevent liquid from flowing back up into the pleural cavity. Vacuum is believed to be beneficial for improving the drainage conditions. However, normal hospital vacuum sources are often not sufficiently reliable to ensure against harmful vacuum levels. Consequently, a reliable vacuum regulator is also advantageous to such a system. Finally, it is advantageous to have a system for collecting the drained fluid so that the amount and nature of this fluid can be monitored.
A number of different systems have developed for pleural drainage. These systems have been classified in an historical sense based on the number of bottles employed in the system. A one-bottle water seal chest drainage system includes a single tube from the patient through a stopper and into a bottle. The tube extends to almost the bottom of the bottle. A vacuum outlet also extends through the stopper into the upper end of the bottle. The bottle is then primed with liquid to create a water seal over the end of the tube from the patient. The one-bottle system is disadvantageous because there is no control over the level of vacuum, there is no control over fluid returning to the pleural cavity, and the amount of head in the bottle cannot be controlled as fluid from the patient causes the water level to rise.
In recognition of certain of the problems of the one-bottle system, a two-bottle system was developed which had a drainage tube from the patient into a collecting chamber. The tube remained above the water level and no water seal was formed in the first bottle. A second tube ran from the first bottle deep into a second bottle. The second bottle was filled over the end of the connecting tube to create a water seal. Another tube then lead from the second bottle to a vacuum chamber. This device also did not protect the patient from excessive vacuum. However, fluid could not return to the pleural cavity and the level of the drainage did not affect the vacuum experienced by the patient.
A classic three-bottle system was developed which incorporated the same mechanism as the two-bottle system with the addition that the second bottle was not hooked to a vacuum source but rather to a third bottle. The third bottle employed a simple vacuum regulator incorporating a tube extending from atmosphere outside the bottle to a position adjacent the bottom. Water was then added to the bottom to create a specific head. Vacuum was then limited by the head in the third bottle. This device eliminated the majority of the difficulties with the simpler systems. However, the amount of tidal air in the first bottle was generally significant in order to provide sufficient capacity for fluid collection. This is considered objectionable by many doctors who preferred the water seal at the tube leading from the patient. For example, an air leak in the fluid collection bottle could pull air into the pleural cavity in a three-bottle system.
Illustrative of the nature of current designs of three bottle systems is a patent to R. E. Bidwell et al., U.S. Pat. No. 3,363,627. This patent is incorporated herein by reference as illustrative of the prior art.
Thus, a number of problems have been resolved with variations in the types of pleural draining systems available. However, certain of the improvements have eliminated beneficial features of the earlier devices. Consequently, the need has long been established for improving on current systems.